A liquid crystal display device is characterized in a low profile, a light weight, and low power consumption, and it is extensively used in various fields. Further, its display performance has greatly advanced with the lapse of time and has gained an advantage over a CRT (Cathode Ray Tube).
A display mode of the liquid crystal display device is determined by how liquid crystal is aligned in cells. In conventional technologies, various display modes are known as display modes of the liquid crystal display device, such as a TN (Twisted Nematic) mode, an MVA (Multi-domain Vertical Alignment) mode, an IPS (In-plane Switching) mode, an OCB (Optically self-Compensated Birefringence) mode, and others.
A large number of liquid crystal display devices using such a display mode are mass-produced. In particular, for example, a liquid crystal display device adopting the TN mode is widely generally used. However, the liquid crystal display device adopting the TN mode can be improved in point of a slow response, a narrow viewing angle, and others.
On the other hand, in the MVA mode, a slit is provided in a pixel electrode of an active matrix substrate, protrusions (ribs) for alignment control over liquid crystal molecules are provided on the opposite electrode of the opposite substrate, and these members form a fringe field to align the liquid crystal molecules in multiple directions. Further, in the MVA mode, a direction along which the liquid crystal molecules tilt by voltage application is divided into multiple directions (multi-domain), thereby achieving a wide viewing angle (see, e.g., Patent Document 1). Furthermore, since the MVA mode is a homeotropic alignment mode, it achieves higher contrast than the TN, IPS, and OCB modes. However, the MVA mode can be improved in point of a complicated manufacturing process and a slow response similarly to the TN mode.
As a display mode other than those described above, there has been proposed a display mode in which a p-type nematic liquid crystal is adopted as a liquid crystal material and a transverse electric field generated by a comb-shaped electrode is utilized to drive the liquid crystal in the homeotropic alignment mode (which will be also referred to as a TBA (Transverse Bend Alignment) mode hereinafter) in order to solve process problems in the MVA mode (see, e.g., Patent Documents 2 to 7).
The TBA mode also has the following characteristics as compared with the MVA mode. First, a high-speed response is possible. Moreover, high contrast based on homeotropic alignment can be achieved. Additionally, a wide viewing angle can be achieved. Further, in the TBA mode, since alignment control using protrusions is not necessary and a pixel configuration is simple, manufacture can be readily performed. That is, a cost can be reduced.
There has been disclosed, as a technique for controlling alignment of a liquid crystal using a fine structure, a technique for forming multiple tilted surfaces facing a predetermined direction on an alignment film surface (see, e.g., Patent Document 8). Further, a technique for forming irregularities whose heights periodically vary on a substrate surface has been disclosed (see, e.g., Patent Document 9).
Moreover, there has been disclosed a method for evaluating an anchoring energy based on a saturation threshold method (see, e.g., Non-Patent Literature 1).
Patent Document 1: JP 11-242225 A
Patent Document 2: JP 57-618 A
Patent Document 3: JP 10-186351 A
Patent Document 4: JP 10-333171 A
Patent Document 5: JP 11-24068 A
Patent Document 6: JP 2000-275682 A
Patent Document 7: JP 2002-55357 A
Patent Document 8: JP 3-150530 A
Patent Document 9: JP 2005-331935 A
Non-Patent Literature 1: Yoshikazu SASAKI and two others, “Surface anchoring energy of liquid crystal with negative dielectric anisotropy determined by saturation voltage method”, Extended Abstracts; The 53rd Spring Meeting of The Japan Society of Applied Physics (Spring in 2006, Musashi Institute of Technology), 2006, p. 1365, No. 23a-P-6